The invention relates to a method of manufacturing a colour display tube comprising an envelope having a display window and, in the envelope, a colour selection electrode have a large number of apertures, and suspension means for suspending the colour selection electrode opposite the display window, a member of each suspension means being fused, at least in part, into the envelope.
Such a method is known from U.S. Pat. No. 4,271,345.
In said patent a method is described in which a pin-shaped member of each suspension means is fused into the display window by means of a heating element which contains a primary and a secondary high-frequency induction coil. The secondary induction coil contains a projecting loop into which the member is partly introduced. The part of the member to be fused into the envelope projects from the loop. By generating a high-frequency electric field in the primary induction coil a high-frequency field is generated in the secondary coil and, hence, also in the loop of the secondary coil. The high-frequency field in the loop heats the part of the member introduced into the loop by means of high-frequency eddy currents generated in the member. Subsequently, the member is fused into the envelope by moving the heating element such that the part of the member projecting from the loop of the secondary coil penetrates into the envelope. A disadvantage of this method is that its efficiency is very low. Only a very small part of the energy is used effectively.